Hydrogen generatior and fuel cell power generation system

ABSTRACT

A body ( 50 ) of a hydrogen generator of the present invention includes a reformer ( 10 ) configured to generate a reformed gas mainly containing hydrogen, a reforming material passage ( 1 ) configured to supply a reforming material, which is a material for a reforming reaction, to the reformer, a CO shifter ( 15 ) configured to convert CO contained in a reformed gas obtained from the reformer ( 10 ) into CO 2 , a reformed gas passage ( 2 ) configured to supply the reformed gas obtained from the reformer ( 10 ) to the CO shifter ( 15 ), and a passage ( 3 ) for the shifted gas obtained from the CO shifter ( 15 ). The shifted gas passage ( 3 ) and the reforming material passage ( 1 ) are adjacent to each other with a shared horizontal wall ( 31 ) interposed therebetween, and thereby, heat from the shifted gas and radiant heat from the downstream end face ( 15   b ) of the CO shifter are transferred to the reforming material that travels in the reforming material passage ( 1 ).

TECHNICAL FIELD

The present invention relates to a hydrogen generator that generates areformed gas mainly containing hydrogen by reforming a hydrocarbon-basedfeed gas such as town gas and LP gas using steam (hereinafter referredto as “steam reforming”), and to a fuel cell system provided with thehydrogen generator.

BACKGROUND ART

A hydrogen generator that generates a reformed gas mainly containinghydrogen by steam-reforming of a hydrocarbon-based feed gas such as towngas and LP gas is used for, for example, producing hydrogen that is usedas a feed gas in a fuel cell. Since the steam reforming reaction(hereinafter simply referred to as “reforming reaction”) in the hydrogengenerator is an endothermic reaction, it is necessary to keep a reformerat a temperature of about 550° C. to 800° C. in order to maintain thereforming reaction. For this reason, in the hydrogen generator, aheating source such as a burner is installed, and a high-temperaturecombustion gas obtained from the heating source, a radiant body thatemits the radiant heat of the combustion gas, or the like, is utilizedto heat the reformer.

Meanwhile, the reformed gas obtained with the reformer of the hydrogengenerator mainly contains hydrogen, as mentioned above, but alsocontains CO as a byproduct produced in the reforming reaction. If such areformed gas containing CO is directly supplied to the fuel cell, the COreduces the reactivity of catalysts in the fuel cell. For this reason,in order to remove CO, a CO shifter that converts CO contained in thereformed gas into CO₂ through a shift reaction is disposed downstream ofthe reformer in the hydrogen generator.

As a conventional hydrogen generator, there is one in which a heatinsulator is arranged along the outer circumference of a wall surface ofa reformer, and a CO shifter is arranged so as to surround the reformerwith the heat insulator interposed therebetween so as to inhibit heatfrom dissipating to outside from the reformer that is heated to a hightemperature as described above (for example, cf. Japanese Patent. No.3108269 (pp. 2-4, FIG. 3)). In addition, there is a hydrogen generatorhaving a configuration in which a plurality of cylindrical units areconcentrically arranged upright, a reformer is formed by filling areforming catalyst into one of the cylinder-shaped clearance spacesformed by wall surfaces of the cylindrical units, and a CO shifter isformed by filling a CO shifting catalyst into a clearance space that islocated on the outer circumference of the reformer; in such aconfiguration, the circumference of the reformer is covered by the COshifter which is kept at a lower temperature (about 180° C. to 400° C.)than that of the reformer, and consequently, heat transfers from thereformer to the CO shifter. As a result, it is possible to decrease heatdissipation to outside (for example, cf. Japanese Laid-Open PatentApplication Publication No. 2002-187705 (pp. 5-10, FIG. 1)).

However, in the hydrogen generators with the above-describedconfigurations, heat transfers mainly from the reformer to the COshifter since the reformer is higher in temperature than the CO shifter,and meanwhile, the heat dissipating from the CO shifter substantiallydoes not transfer to the reformer. Thus, the heat that has dissipatedfrom the CO shifter cannot be utilized effectively by returning it tothe reformer, and as a result, sufficiently high thermal efficiencycannot be attained.

DISCLOSURE OF THE INVENTION

In view of such problems in conventional hydrogen generators, it is anobject of the present invention to provide a hydrogen generator in whichthermal efficiency is improved, and a fuel cell system comprising thehydrogen generator.

In order to achieve the foregoing and other objects, the presentinvention provides a hydrogen generator comprising a reformer configuredto generate a reformed gas mainly containing hydrogen from a reformingreaction material through a reforming reaction, a reforming materialpassage configured to supply the reforming reaction material to thereformer, a carbon monoxide shifter configured to convert carbonmonoxide in the reformed gas into carbon dioxide, a reformed gas passageconfigured to supply the reformed gas from the reformer to the carbonmonoxide shifter, and a shifted gas passage configured to take out ashifted gas obtained from the carbon monoxide shifter, the hydrogengenerator being configured to perform heat exchange between the shiftedgas passage and the reforming material passage.

In such a configuration, the temperature of the shifted gas passage sideis kept at about 180° C. to 400° C., while the temperature of thereforming material passage side is kept at about 110° C. to 120° C.Accordingly, here, heat transfers from the shifted gas passage side tothe reforming material passage side, and by the just-noted heat, thereforming reaction material traveling inside the reforming materialpassage is heated. In this way, this configuration makes it possible toutilize the heat of the reformed gas shifter, which has not beeneffectively utilized sufficiently in the past, for heating the reformingreaction material, and therefore can improve thermal efficiency.

A heat generating portion of the carbon monoxide shifter may configuredto face a wall portion of the shifted gas passage with a spaceinterposed therebetween. Or, heat retained by a shifted gas obtainedfrom the carbon monoxide shifter may be supplied to the reformingmaterial gas passage via the shifted gas passage.

It is preferable that the reforming material passage be arranged moreinward of the hydrogen generator than the shifted gas passage.

With such a configuration, heat transfers from the shifted gas passagetowards the interior of the hydrogen generator, and therefore, itbecomes possible to trap the heat generated by the shift reaction in thecarbon monoxide shifter into the interior of the hydrogen generator.

It is also possible to employ a configuration wherein: an interior of abody of the hydrogen generator is partitioned by a plurality ofaxially-directed walls sharing a central axis and arranged opposing toone another at predetermined gaps, and by a plurality ofradially-directed walls arranged at a predetermined end portion of theaxially-directed walls so as to intersect with the axially-directedwalls, so that the reforming material passage, the reformed gas passage,and the shifted gas passage are formed in the body, the reformer isformed along the central axis, and the carbon monoxide shifter is formedin the axial direction side of the reformer; the reforming materialpassage is arranged so as to surround an outer side of the reformer, oneend portion thereof is connected to one end face of the reformer in theaxial direction, and at least a portion thereof is formed along one endface of the reformer in the axial direction; the reformed gas passage isarranged so as to surround an outer circumference of the reformer, oneend portion thereof is connected to the other end face of the reformerin the axial direction, and another end portion thereof is connected toan upstream face of the carbon monoxide shifter; the carbon monoxideshifter is arranged so as to oppose the one end face of the reformer inthe axial direction with the reforming material passage interposedtherebetween; and the shifted gas passage is connected to a downstreamend face of the carbon monoxide shifter at one end portion thereof, andbetween the carbon monoxide shifter and the reformer opposing eachother, the shifted gas passage is directly or indirectly in contact witha portion of the reforming material passage that is along the end faceof the reformer.

With such a configuration, it is possible to realize a configuration inwhich the carbon monoxide shifter is arranged so as to oppose an endface of the reformer at the axial direction side of the reformer, andthe shifted gas passage connected to the shifter and the reformingmaterial passage connected to the end face of the reformer are adjacentto each other. Moreover, with such a configuration, the shifted gas isdischarged toward the reformer side arranged inward of the hydrogengenerator; therefore, it becomes possible to trap the heat obtainedthrough the shift reaction within the interior of the hydrogengenerator.

It is also possible to employ a configuration wherein: an interior of abody of the hydrogen generator is partitioned by a plurality ofaxially-directed walls sharing a central axis and arranged opposing toone another at predetermined gaps, and by a plurality ofradially-directed walls arranged at a predetermined end portion of theaxially-directed walls so as to intersect with the axially-directedwalls, so that the reforming material passage, the reformed gas passage,and the shifted gas passage are formed in the body, the reformer isformed along the central axis, and the carbon monoxide shifter is formedso as to surround an outer side of the reformer in the axial direction;the reforming material passage is arranged so as to surround an outerside of the reformer, and one end portion thereof is connected to oneend face of the reformer in the axial direction; the reformed gaspassage is arranged so as to surround an outer side of the reformingmaterial passage in the axial direction, one end portion thereof isconnected to the other end face of the reformer in the axial direction,and the other end portion thereof is connected to an upstream face ofthe carbon monoxide shifter; the carbon monoxide shifter is positionedbetween the reformed gas passage and the reforming material passage andis arranged so as to surround the reforming material passage in theaxial direction; and the shifted gas passage is connected to adownstream end face of the carbon monoxide shifter at one end portionthereof, the shifted gas passage is directly or indirectly in contactwith the reforming material passage between the carbon monoxide shifterand the reformer, and the shifted gas passage surrounds an outer side ofthe reforming material passage in the axial direction.

With such a configuration, it is possible to realize a configuration inwhich the carbon monoxide shifter is arranged so as to surround theouter side of the reformer with the reforming material passageinterposed therebetween, and the shifted gas passage connected to theshifter is adjacent to the reforming material passage. Moreover, withsuch a configuration, the shifted gas is discharged toward the reformerarranged inward of the hydrogen generator; therefore, it becomespossible to trap the heat obtained through the shift reaction within theinterior of the hydrogen generator.

It is preferable that the configuration is such that the shifted gas isblown out from the downstream end face of the carbon monoxide shifterinto the shifted gas passage so as to collide with, at the portion wherethe shifted gas passage and the reforming material passage are incontact, a partition wall that partitions both of the passages, andthereafter, the shifted gas travels along the shifted gas passage.

With such a configuration, since the blowing direction of the shiftedgas intersects with the traveling direction of the reforming reactionmaterial traveling in the reforming material passage, no heat transferlaminar film forms when heat transfers from the shifted gas passage sideto the reforming material passage side; consequently, it becomespossible to perform heat exchange more effectively.

It is preferable that, in the carbon monoxide shifter, a gas travelingdirection from the upstream face toward the downstream end face issubstantially a vertical direction.

With such a configuration, gas travels along substantially a verticaldirection in the carbon monoxide shifter, and therefore, due to theeffect of buoyancy, a uniform radiant face is formed on the downstreamend face of the carbon monoxide shifter and the traveling of the gas isaccelerated. Therefore, effective heat exchange becomes possible.

The reforming reaction material may contain a hydrocarbon-based feed gasand water, and the reforming material passage may comprise a passageportion in which the feed gas and water travel in different phasestates, a water evaporator configured to evaporate the water to producesteam, and a feed gas mixture passage portion in which a gas mixture ofthe feed gas and the steam travels; and the reforming material passagethat is directly or indirectly in contact with the shifted gas passagemay be any of: the feed gas mixture passage portion; the passage portionin which the feed gas and water travel in different phase states; thefeed gas passage portion; and the water passage portion.

The carbon monoxide shifter may such that a platinum group metal servingas a shift catalyst is carried on a carrier composed of a metal oxidecontaining at least one selected from Al, Ce, and Zr.

In such a configuration, since the carrier is composed of a metal oxidecontaining Al, Ce, or Zr, the heat resistance of the carbon monoxideshifter further improves. Consequently, the temperature of the shiftercan be further increased. As a result, the amount of heat supplied fromthe shifted gas passage side is increased, and the advantageous effectsattained by the present invention are exhibited more effectively.

It is possible to employ a configuration in which heat exchange isperformed between the reformed gas passage and the reforming materialpassage.

With such a configuration, heat is supplied from the shifted gas passageto the reforming material passage, and heat is also supplied from thereformed gas passage to the reforming material passage. Therefore, it ispossible to achieve a further improvement in thermal efficiency. Inparticular, since heat supply is made possible from the reformer that iskept at a high temperature of about 550° C. to 800° C., the reformingreaction material in the reforming material passage can be effectivelyheated. Moreover, by giving heat retained by the reformed gas to thereforming reaction material, the temperature of the reformed gas can becontrolled to an optimum reaction temperature in the carbon monoxideshifter.

The fuel cell system according to the present invention comprises ahydrogen generator having any one of the foregoing configurations; and afuel cell configured to generate power using a fuel gas and an oxidizinggas, the fuel gas containing hydrogen as its main component and beingsupplied from the hydrogen generator.

With such a configuration, an improvement in thermal efficiency isachieved in the hydrogen generator as described above, and therefore, itbecomes possible to realize a fuel cell system in which thermalefficiency is improved as a whole.

The foregoing and other objects, features and advantages of the presentinvention will become more readily apparent from the following detaileddescription of preferred embodiments of the invention, with reference tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating theconfiguration of a hydrogen generator according to Embodiment 1 of thepresent invention.

FIG. 2 is a schematic cross-sectional view illustrating theconfiguration of a hydrogen generator according to Embodiment 2 of thepresent invention.

FIG. 3 is a schematic cross-sectional view illustrating theconfiguration of a hydrogen generator according to Embodiment 3 of thepresent invention.

FIG. 4 is a schematic cross-sectional view illustrating theconfiguration of a hydrogen generator according to Embodiment 4 of thepresent invention.

FIG. 5 is a schematic configuration view of a fuel cell system accordingto Embodiment 1 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, preferred embodiments of the present invention aredescribed with reference to the drawings. It should be noted that thedrawings show characteristic configurations of hydrogen generators andfuel cell systems provided with the hydrogen generators according to theembodiments, and the graphical representations and detailed explanationsof the configurations that have been known conventionally will beomitted.

Embodiment 1

[Hydrogen Generator]

FIG. 1 is a cross-sectional view schematically illustrating theconfiguration of a hydrogen generator according to Embodiment 1 of thepresent invention.

As shown in FIG. 1, the hydrogen generator mainly comprises acylindrical-shaped body 50 the upper and lower ends of which are closed,a burner 20 to which a tubular-shaped radiant cylinder 21 is attached,and a heat insulator 53 that covers the outer circumference of the body50. Hereinbelow, the structure of the hydrogen generator is described indetail.

The burner 20, to which the radiant cylinder 21 is attached, isaccommodated and arranged at the center of the body 50 so that itscentral axis matches that of the body 50. The inside of thecylindrical-shaped body 50, specifically, the space between the innerwall of the body 50 and the radiant cylinder 21, is partitioned by aplurality of tubular-shaped concentric vertical walls 102 that havevarious different radii and axial lengths, and a plurality ofdisk-shaped or hollow disk-shaped horizontal walls 103 that are disposedas appropriate at predetermined end portions of the vertical walls 102.Specifically, the plurality of vertical walls 102 is concentricallyarranged upright inside the body 50 to form a clearance space 51 betweenthe vertical walls 102, and, a predetermined end portion of the verticalwalls 102 is closed as appropriate by the horizontal walls 103 so thatdesired gas passages are formed utilizing the clearance space 51.Thereby, a reformer 10, a CO shifter 15, and various gas passages areformed in the interior of the body 50.

The gas passages are formed to have ring shape within the cross sectionI-I′ along a radial direction of the body 50, and upstream passages 11,30 of a reforming material passage 1 having a double structure, adownstream passage 41 of a combustion gas passage 4 having a doublestructure, a reformed gas passage 2, the reformer 10, and an upstreampassage 42 of the combustion gas passage 4 are disposed in that orderfrom the outer side toward the inner side.

The reformer 10 has a cylinder-like shape, and is arranged so as tosurround the side part and the top part of the radiant cylinder 21 withthe upstream passage 42 of the combustion gas passage 4 interposedtherebetween. A downstream passage 30′ of the reforming material passage1 is formed axially upward of the reformer 10, along the upper end faceof the reformer 10 by a horizontal wall 103 (hereinafter this horizontalwall 103 is specifically referred to as “horizontal wall 31”). A COshifter 15 is disposed further axially upward from the reformer 10 ontop of the horizontal wall 31 so as to oppose the upper end face of thereformer 10. By the horizontal wall 31 and a downstream end face 15 b ofthe CO shifter 15, a shifted gas passage 3 is formed. Here, the COshifter 15 and the reformer 10 are arranged opposed to each other andthe clearance space between them is partitioned by the horizontal wall31 as described above, whereby the above-mentioned downstream passage30′ and a shifted gas passage 3, formed so as to sandwich the horizontalwall 31 therebetween, are directly in contact with each other with thehorizontal wall 31 interposed therebetween.

The body 50 having the above-described configuration is provided with: amaterial feed port 5 and a water supply port 6 of the reforming materialpassage 1; a gas outlet port 7 of the shifted gas passage 3; and anexhaust gas outlet port 8 of the combustion gas passage 4, all of whichcommunicate with the outside of the hydrogen generator. Also, the burner20 attached to the body 50 is provided with an air supply port 20 a anda fuel supply port 20 b.

With the combustion gas passage 4, an end portion of the upstreampassage 42 is connected to the burner 20, to which the radiant cylinder21 is attached, and an end portion of the downstream passage 41 isconnected to outside through the exhaust gas outlet port 8. Also, withthe reforming material passage 1, an end portion of the upstream passage11 is connected to outside through the material feed port 5 and thewater supply port 6, and an end portion of the downstream passage 30(30′) is connected to the upper end face of the reformer 10.Furthermore, with the reformed gas passage 2, its upstream end portionis connected to a lower end face of the reformer 10, and its downstreamend portion is connected to an upstream end face 15 a of the CO shifter15. Also, the upstream end portion of the shifted gas passage 3 isconnected to a downstream end face 15 b of the CO shifter 15, and thedownstream end portion is connected to outside through the shifted gasoutlet port 7.

The reformer 10 is formed in a manner that one in which a platinum groupmetal serving as a reforming catalyst is carried on a carrier made of ametal oxide shaped into a granular form is filled into the clearancespace 51 formed between the vertical walls 102. Thus, the reformer 10 isformed more inward than the reforming material passage 1 and thereformed gas passage 2 in the hydrogen generator, and its upper end faceis connected to the reforming material passage 1 while its lower endface is connected to the reformed gas passage 2.

The CO shifter 15 has a configuration such that a platinum group metalserving as a shift catalyst is dispersed and carried on a carriercomposed of a film-state metal oxide formed on a ceramic honeycombsubstrate.

The outer circumference of the body 50 and the burner 20 is covered witha heat insulator 53 except for the areas of the material feed port 5,the water supply port 6, the shifted gas outlet port 7, the combustionexhaust gas outlet port 8, the air supply port 20 a, and the fuel supplyport 20 b, which communicate with outside.

Next, the operation of the above-described hydrogen generator isdescribed.

A fuel gas is supplied to the burner 20 through the fuel supply port 20b, and air is supplied to the burner 20 through the air supply port 20a. Here, as will be described later with FIG. 5, an excessive fuel(so-called off gas) obtained in the fuel cell system is used as a fuelgas. Then, using the fuel gas and the air supplied, diffusion combustionis performed. Here, since the burner 20 is surrounded by the radiantcylinder 21, the just-noted combustion is performed within the radiantcylinder 21, by which a high-temperature combustion gas is produced. Theheat of the combustion gas is transferred radially outward with respectto the body 50 through the radiant cylinder 21 by radiation. Suchradiant heat heats up the reforming catalyst of the reformer 10, and atthe same time, the combustion gas travels axially upward in the radiantcylinder 21, directly heating up the reforming catalyst. Thereby, thereformer 10 is kept at a temperature in the range of about 550° C. to800° C. The combustion gas that has ascended travels axially downwardthrough the upstream passage 42 of the combustion gas passage 4 along avertical wall 102, further travels axially upward through the downstreampassage 41, and is finally discharged outside from the combustionexhaust gas outlet port 8 (arrow i in the figure). Here, as will bedescribed later, heat exchange takes place between the heat retained bythe combustion gas and the water traveling through the reformingmaterial passage 1 during the process in which the combustion gastravels through the combustion gas passage 4, and the heat of thecombustion gas is utilized as latent heat of vaporization in an waterevaporator 9.

A feed gas containing a compound composed of at least carbon andhydrogen (for example, hydrocarbon gas such as town gas or LP gas, oralcohol such as methanol), which is supplied from the material feed port5, and water, which is supplied from the water supply port 6, are sentthrough the reforming material passage 1 to the reformer 10, as areforming reaction material. Here, first, the feed gas and the watersupplied from respective supply ports 5 and 6 travel axially downwardthrough the upstream passage 11 of the reforming material passage 1along the vertical walls 102 (arrow a in the figure) in different phasestates (i.e., gas and liquid). Then, in the water evaporator 9positioned at a bottom portion of the passage 11, water evaporatesutilizing the heat retained by the combustion gas and the radiant heatas well as the later-described heat from the reformer 10, and turns intosteam. Further, a mixture of the steam and the above-noted feed gas(hereafter this mixture is referred to as a “feed gas mixture”) travelsaxially upward through the upstream passage 30 along the vertical walls102 (arrow b in the figure). Then, the feed gas mixture enters adownstream passage 30′ of the reforming material passage 1, which isformed along the upper end face of the reformer 10, then travels throughthe passage 30′ radially inward of the body along the horizontal wall31, and is subsequently supplied into the reformer 10 (arrow c in thefigure). The temperature of the feed gas mixture in such a supplyprocess is about 110° C. to 120° C. Herein, the downstream passage 30′of the reforming material passage 1 through which the feed gas mixturetravels as described above is specifically referred to as a feed gasmixture passage portion 30′.

The feed gas mixture is introduced from the upper end face of thereformer 10 into the interior thereof, and travels axially downwardthrough the reforming catalyst along the vertical walls 102 (arrow d inthe figure). During this travel, the feed gas mixture is heated and itstemperature is elevated, whereby a reforming reaction is performed,generating a reformed gas. The reformed gas mainly contains hydrogen andalso contains CO produced as a byproduct. The generated reformed gas isdischarged from the lower end face of the reformer 10 to the reformedgas passage 2, and travels axially upward through the passage along thevertical walls 102 (arrow e in the figure). Then, it travels in radialdirections along the horizontal wall 103 through the passage and reachesthe CO shifter 15 (arrow f in the figure).

The reformed gas supplied onto the upstream end face 15 a of the COshifter 15 travels axially (in a vertical direction) downward throughthe shift catalyst of the shifter 15. In this process, a reaction bywhich the CO contained in the reformed gas is converted into CO₂, i.e.,a shift reaction, is performed, whereby a shifted gas is produced. Theshifted gas is blown vertically downward from the downstream end face 15b of the CO shifter 15 into the shifted gas passage 3 (arrow g in thefigure), and collides with the bottom face of the passage 3, that is,the horizontal wall 31 shared with the feed gas mixture passage portion30′. Thereafter, the shifted gas travels in radial directions along thehorizontal wall 103 through the passage, then travels axially upwardthrough the passage along the vertical walls 102, and is taken out fromthe gas outlet port 7 (arrow h in the figure).

[Fuel Cell System]

FIG. 5 is a schematic configuration view of a fuel cell system accordingto the present embodiment, which is provided with a hydrogen generatoras shown in FIG. 1.

This fuel cell system comprises the hydrogen generator 150 shown in FIG.1 and a fuel cell 151. Here, in the hydrogen generator 150, a COpurifier 40 is provided downstream of the CO shifter 15. The COconcentration in the shifted gas obtained from the CO shifter 15 isreduced to between ⅕ and 1/50 of the CO concentration in the reformedgas, according to the temperature of the shift reaction. Nevertheless,it is necessary that the CO concentration in a fuel gas supplied to thefuel cell is reduced to 10 ppm or less. Therefore, the shifted gas isfurther processed by being supplied to the CO purifier 40 arrangeddownstream of the CO shifter 15. Then, the gas obtained by the hydrogengenerator 150, which mainly contains hydrogen, is supplied to the anodeof the fuel cell 151 as a fuel gas. In the fuel cell 151, powergeneration is performed utilizing a reaction between the fuel gassupplied to the anode and an oxygen gas supplied to the cathode. Then,the fuel gas that has not been used in the reaction is supplied as anoff gas to the burner of the hydrogen generator, where it is burnt.

As described above, according to the present embodiment, heat isgenerated in the CO shifter 15 accompanying the shift reaction since theshift reaction is an exothermic reaction, forming a heat generatingportion in the CO shifter 15. In addition, the reformed gas supplied tothe CO shifter itself retains heat. Therefore, the temperature of the COshifter 15 and of the shifted gas is kept at a temperature of about 180°C. to 400° C. In particular, because the shift reaction, which is anexothermic reaction, is performed as described above, the temperature ofthe CO shifter 15 is higher at the downstream end face 15 b than at theupstream end face 15 a.

In the present embodiment, the shifted gas passage 3 arranged on thedownstream end face 15 b of the CO shifter 15 is directly in contactwith the feed gas mixture passage portion 30′ via the horizontal wall31, and moreover, as described above, the temperature of the feed gasmixture that flows through the feed gas mixture passage portion 30′ isabout 110° C. to 120° C. while the temperature of the shifted gas thatflows through the shifted gas passage 3 is about 180° C. to 400° C.Consequently, heat transfers from the shifted gas to the feed gasmixture via the horizontal wall 31, to perform heat exchange. In such aheat exchange, the shifted gas forms such a stream as to collide withthe horizontal wall 31 as described above, and therefore, no heattransfer laminar film is formed in the vicinity of the horizontal wall31; as a consequence, a higher heat exchange efficiency can be obtainedin comparison with the case in which the shifted gas forms a counterflow or a parallel flow which does not collide with the horizontal wall31.

Moreover, in addition to the heat retained by the shifted gas, theradiant heat from the CO shifter 15 is supplied to the feed gas mixturethrough the shifted gas passage 3. Here, since the gas flow direction inthe CO shifter 15 is directed vertically downward, a uniform radiantface is formed on the downstream end face 15 b of the CO shifter 15 dueto the effect of buoyancy. For this reason, in the CO shifter 15,radiant heat uniformly dissipates from the downstream end face 15 b,which has a higher temperature than the upstream end face 15 a asdescribed above, and heat is effectively supplied to the feed gasmixture through the horizontal wall 31.

Thus, the hydrogen generator of the present embodiment makes it possibleto perform heat recovery by utilizing the heat from the reformer 10 forevaporating water and heating the feed gas mixture, and moreover, toperform heat recovery by utilizing the heat retained by the shifted gasobtained from the CO shifter 15 and the radiant heat of the CO shifter15 for heating the feed gas mixture. Therefore, the present embodimentachieves an improvement in a heat recovery amount over conventionalcases.

Furthermore, such a configuration also attains the effect of trappingthe heat generated by the shift reaction within the interior of thehydrogen generator, because the shifted gas is discharged toward thereformer 10 arranged inside the hydrogen generator. Thus, since anefficient heat recovery becomes possible with the hydrogen generator,the use of the hydrogen generator for a fuel cell system makes itpossible to achieve an improvement in thermal efficiency of the systemas a whole.

Here, in the foregoing, the reformer 10 has a configuration in which aplatinum group metal is carried on a carrier of a metal oxide shapedinto a granular form, as described above, but the configuration of thereformer 10 may be other than this configuration. For example, dependingon the shape of the reformer 10, such a configuration is also possiblethat a platinum group metal is dispersed on a carrier made of afilm-state metal oxide formed on a honeycomb substrate of ceramic,metal, or the like.

Furthermore, in the foregoing, the CO shifter 15 has a configuration inwhich a platinum group metal is dispersed and carried on a film-statemetal oxide carrier formed on a ceramic honeycomb substrate, but theconfiguration of the CO shifter 15 may be other than this configuration.For example, the substrate may be a structure constructed by a metallicthin plate of stainless steel or the like; moreover, such aconfiguration is possible that, depending on the shape of the CO shifter15, a platinum group metal carried on a carrier of a metal oxide shapedinto a granular form is filled. Further, as the shift catalyst of the COshifter 15, a base metal such as a Cu—Zn type metal may be used otherthan the platinum group metal. It should be noted that the catalyst hasa higher heat resistance when a platinum group metal is used as thecatalyst, as in the present embodiment, than when a base metal is usedas the catalyst, and consequently, the temperature of the CO shifter 15can be made higher. Therefore, the temperature difference becomesgreater between the feed gas mixture and the CO shifter 15 and betweenthe feed gas mixture and the shifted gas, and consequently, the heatrecovery amount from the CO shifter 15 and the shifted gas to the feedgas mixture becomes greater.

Moreover, the present embodiment has a configuration in which the COshifter 15 is arranged axially above the burner 20 and the surroundingreformer 10; however, as a modified example of the present embodiment,such a configuration is possible in which axial positions of the COshifter 15 and the reformer 10 are reversed, in other words, the burner20 and the reformer 10 are arranged axially above the CO shifter 15.With such a configuration, the speed at which the shifted gas collideswith the horizontal wall 31 increases due to the effect of buoyancy,making it possible to perform heat exchange more efficiently.

Embodiment 2

[Hydrogen Generator]

FIG. 2 is a cross-sectional view schematically illustrating theconfiguration of a hydrogen generator according to Embodiment 2 of thepresent invention. The hydrogen generator of the present embodiment hasa similar configuration to that of the hydrogen generator of Embodiment1, but it differs from Embodiment 1 in the following points.

Embodiment 1 has a configuration in which the feed gas mixture passageportion 30′ located further downstream from the water evaporator 9, thatis, a region through which a mixture of steam and feed gas flows, isarranged so as to be adjacent to the shifted gas passage 3; in contrast,in the present embodiment, a region of the reforming material passage 1that is further upstream from the water supply port 6, that is, a regionthrough which only feed gas flows (hereafter this region is referred toas a “feed gas passage portion 32”) is arranged so as to be adjacent tothe shift gas passage 3 with a shared horizontal wall 33 interposedtherebetween.

Specifically, in the present embodiment, the upstream passage 11 of thereforming material passage 1 includes the feed gas passage portion 32,which is partitioned by a horizontal wall 103 and arranged axially abovethe feed gas mixture passage portion 30′ so as to oppose the passageportion 30′. In addition, the feed gas passage portion 32 is directly incontact with the shifted gas passage 3 with the horizontal wall 33interposed therebetween. The downstream of the feed gas passage portion32 has the same configuration as that of Embodiment 1.

In such a configuration, the feed gas that has been supplied from thematerial feed port 5 travels in radial directions along the horizontalwall 103 through the feed gas passage portion 32, and thereafter travelsaxially downward along the vertical walls 102 through the upstreampassage 11 of the reforming material passage 1. Meanwhile, water issupplied from the water supply port 6 in a region further downstreamfrom the feed gas passage portion 32, and the water is turned into steamat the water evaporator 9 and is mixed with a feed gas in a similarmanner to that in Embodiment 1. The feed gas mixture, in which the steamand the feed gas are mixed, flows through the interior of the feed gasmixture passage 30 of the reforming material passage 1 in a similarmanner to that in Embodiment 1 and is guided to the reformer 10.

Here, between the shifted gas and the feed gas flowing through therespective passages in the shifted gas passage 3 and the feed gaspassage portion 32 that are adjacent to each other as in the presentembodiment, the shifted gas has a higher temperature than the feed gas.Consequently, the heat retained by the shifted gas and the radiant heatfrom the CO shifter 15 are transferred to the feed gas flowing throughthe feed gas passage portion 32 via the shared horizontal wall 33, andutilized for heating the feed gas. In such a heat exchange between theshifted gas and the feed gas, the shifted gas forms such a stream as tocollide with the horizontal wall 33 shared with the feed gas passageportion 32, as in the case of Embodiment 1, and therefore, as wasdescribed in the foregoing, it becomes possible to transfer heat to thefeed gas efficiently. Moreover, in this case as well as in the case ofEmbodiment 1, a uniform radiant face is formed on the downstream endface 15 b of the CO shifter 15 due to the effect of buoyancy, and theradiant heat is transferred from the downstream end face 15 b, which hasa higher temperature than the upstream end face 15 a, to the feed gaseffectively.

As described above, the hydrogen generator of the present embodimentmakes it possible to perform heat recovery utilizing the heat of theshifted gas obtained from the CO shifter 15 for heating the feed gas.Accordingly, thermal efficiency is improved over conventional cases, aswith Embodiment 1.

In the present embodiment as well as in Embodiment 1, the configurationsof the CO shifter 15 and the reformer 10 are not limited to, but may beother than, the above-described configurations. In addition, as amodified example of the present embodiment, a configuration may beemployed in which the vertical positions of the CO shifter 15 and thereformer 10 are reversed, like the modified example of Embodiment 1. Inthis case as well, the similar advantageous effects as the foregoing areattained.

[Fuel Cell System]

A fuel cell system according to the present embodiment is such that thefuel cell system of Embodiment 1 (FIG. 5) comprises the hydrogengenerator of the present embodiment in place of the hydrogen generatorof Embodiment 1. This makes it possible to construct a fuel cell systemcomprising a hydrogen generator that can achieve the foregoingadvantageous effects.

Embodiment 3

[Hydrogen Generator]

FIG. 3 is a cross-sectional view schematically illustrating theconfiguration of a hydrogen generator according to Embodiment 3 of thepresent invention. The hydrogen generator of the present embodiment hasa similar configuration to that of the hydrogen generator of Embodiment1, but it differs from Embodiment 1 in the following points.

In the present embodiment, a region of the reforming material passage 1that is at the further upstream side from the material feed port 5, thatis, a region though which only water flows (hereafter referred to as a“water passage portion 34”) is arranged so as be indirectly adjacent tothe shifted gas passage 3 with a heat transfer inhibiting structure 35interposed therebetween. In addition, with the reforming materialpassage 1 of the present embodiment, a feed gas is supplied from thematerial feed port 5 in a region further downstream from the waterpassage portion 34. The feed gas is mixed with steam generated by thewater evaporator 9, and the resultant feed gas mixture is guided to thereformer 10 as in a similar manner to Embodiment 1.

Specifically, in the present embodiment, the upstream passage 11 of thereforming material passage 1 includes the water passage portion 34,which is partitioned by a horizontal wall 103 and is arranged axiallyabove the feed gas mixture passage portion 30′ so as to oppose thepassage portion 30′. In addition, the water passage portion 34 isindirectly in contact with the shifted gas passage 3 with the horizontalwall 36 and the heat transfer inhibiting structure 35 interposedtherebetween. The configuration of the downstream of the water passageportion 34 is the same as that of Embodiment 1.

In such a configuration, water supplied from the water supply port 6travels in radial directions along the horizontal wall 103 through thewater passage portion 34, and thereafter, travels axially downward alongthe vertical walls 102 through the upstream passage 11 of the reformingmaterial passage 1. Meanwhile, a feed gas is supplied from the materialfeed port 5 in a region further downstream from the water passageportion 34. The water that has traveled through the passage turns intosteam in the water evaporator 9 and is mixed with the feed gas in asimilar manner to that in Embodiment 1. The feed gas mixture, in whichthe steam and the feed gas are mixed, flows through the interior of thefeed gas mixture passage portion 30′ of the reforming material passage 1in a similar manner to that in Embodiment 1, and is guided to thereformer 10.

Here, between the shifted gas and the water in the shifted gas passage 3and the water passage portion 34 that are indirectly adjacent to eachother as in the present embodiment, the shifted gas has a highertemperature than the water. Therefore, the heat retained by the shiftedgas and the radiant heat from the CO shifter 15 are transferred to thewater flowing through the water passage portion 34 via the heat transferinhibiting structure 35. In this case, the heat transferred from the COshifter 15 side to the water passage portion 34 side is adjusted by theheat transfer inhibiting structure 35 to be a heat amount such as not tocause the water to evaporate. Examples of the heat transfer inhibitingstructure 35 used include a heat insulator such as glass wool in which ametal having a higher thermal conductivity is dispersed and mixed, aspace in which particles of ceramic or the like are filled, and a spacein which a material that absorbs heat by a phase change and causeslittle temperature rise is filled.

In the heat exchange between the shifted gas and the water in thepresent embodiment, the shifted gas forms a stream such as to collidewith the horizontal wall 36, which is the bottom face of the shifted gaspassage 3, as in the case of Embodiment 1. This makes it possible totransfer heat to the water efficiently, as in Embodiment 1. Furthermore,as in the case of Embodiment 1, in the CO shifter 15, the radiant heatis transferred to the water effectively from the downstream end face 15b, which has a higher temperature than the upstream end face 15 a, dueto the effect of buoyancy.

As has been described above, the hydrogen generator of the presentembodiment makes it possible to perform heat recovery utilizing the heatof the shifted gas obtained from the CO shifter 15 for heating water.Consequently, thermal efficiency is improved over conventional cases, asin Embodiment 1.

In the present embodiment as well as in Embodiment 1, the configurationsof the CO shifter 15 and the reformer 10 are not limited to, but may beother than, the above-described configurations. In addition, as amodified example of the present embodiment, a configuration may beemployed in which the vertical positions of the CO shifter 15 and thereformer 10 are reversed.

[Fuel Cell System]

A fuel cell system according to the present embodiment is such that thefuel cell system of Embodiment 1 (FIG. 5) comprises the hydrogengenerator of the present embodiment in place of the hydrogen generatorof Embodiment 1. This makes it possible to construct a fuel cell systemcomprising a hydrogen generator that can achieve the foregoingadvantageous effects.

Embodiment 4

[Hydrogen Generator]

FIG. 4 is a cross-sectional view schematically illustrating theconfiguration of a hydrogen generator according to Embodiment 4 of thepresent invention. The hydrogen generator of the present embodiment hassimilar constituting elements to those of the hydrogen generator ofEmbodiment 1, but its structure is different from Embodiment 1 in thefollowing points.

Specifically, in Embodiment 1, the CO shifter 15 and the shifted gaspassage 3 are arranged above the reformer 10 in the axial direction ofthe hydrogen generator; in contrast, in the present embodiment, acylindrical-shaped CO shifter 15′ and a shifted gas passage 3 arearranged in a radial direction of the hydrogen generator so as tosurround the outer circumference of the reformer 10, and a feed gasmixture passage portion 30′ of the reforming material passage 1 isarranged between the reformer 10 and the shifted gas passage 3.

Specifically, in the present embodiment, the interior of acylindrical-shaped body 50, the upper and lower ends of which areclosed, is partitioned by vertical walls 102 and horizontal walls 103 ina similar manner to that in Embodiment 1, and thereby, acylindrical-shaped reformer 10 is formed in the center of the hydrogengenerator so as to surround a burner 20 to which a radiant cylinder 21is attached. In addition, gas passages and a CO shifter 15′, each ofwhich has a cylindrical shape and a ring-like cross-sectional shapetaken along line II-II′ in a radial direction of the hydrogen generator,are formed so as to surround the reformer 10.

Here, a downstream passage 41 of a combustion gas passage 4 having adouble structure, dual-structured upstream passages 11 and 30 of areforming material passage 1 having a triple structure, a downstreampassage 23 of a reformed gas passage 2 having a double structure, a COshifter 15′, a shifted gas passage 3, a downstream passage 30′ of thereforming material passage 1, an upstream passage 22 of the reformed gaspassage 2, a reformer 10, and an upstream passage 42 of a combustion gaspassage 4 are formed in that order from the outer side toward the innerside in a radial direction of the hydrogen generator. The above-notedupstream passages and downstream passages of the passages havingmultiple structures are connected by passages formed by the horizontalwalls 103 in a radial direction.

The above-described gas passages are as follows. As for the combustiongas passage 4, an end portion of the upstream passage 42 is connected tothe burner 20, to which the radiant cylinder 21 is attached, and an endportion of the downstream passage 41 is connected to outside through anexhaust gas outlet port 8. As for the reforming material passage 1, anend portion of the upstream passage 11 is connected to outside through amaterial feed port 5 and a water supply port 6, and an end portion ofthe downstream passage 30′ is connected to a lower end face of thereformer 10. In addition, as for the reformed gas passage 2, an endportion of the upstream passage 22 is connected to an upper end face ofthe reformer 10 and an end portion of the downstream passage 23 isconnected to an upstream end face 15′a of the CO shifter 15′. Inaddition, as for the shifted gas passage 3, its upstream end portion isconnected to a downstream end face 15′b of the CO shifter 15′, and itsdownstream end portion is connected to outside through a shifted gasoutlet port 7.

In the present embodiment, the CO shifter 15′ is unlike the CO shifter15 of Embodiment 1, in which a platinum group metal is carried on afilm-state metal oxide carrier formed on a honeycomb substrate, but isformed by arranging one in which a platinum group metal is carried on ametal oxide carrier shaped into a granular form, in a cylindrical-shapedregion between the reformed gas passage 2 and the shifted gas passage 3.

In the present embodiment, a feed gas and water respectively suppliedfrom the material feed port 5 and the water supply port 6 flow axiallydownward along the vertical walls 102 through the upstream passage 11,which is on the outer side of the reforming material passage 1 (arrow Ain the figure). Then, the water evaporates in a water evaporator 9 in abottom portion of the passage, receiving heat from the reformer 10 andthe combustion gas inside the combustion gas passage 4. The steam thusgenerated and the feed gas are mixed, forming a feed gas mixture, whichflows axially upward along the vertical walls 102 through the upstreampassage 30 (arrow B in the figure). Thereafter, it enters the downstreampassage 30′ and again flows axially downward along the vertical walls102 through the passage. Here, the downstream passage 30′ of thereforming material passage 1 through which the feed gas mixture flows isspecifically referred to as a feed gas mixture passage portion 30′.Through the feed gas mixture passage portion 30′, the feed gas mixtureis supplied from the lower end of the reformer 10 into the interior ofthe reformer 10 (arrow C in the figure). The feed gas mixture undergoesa reforming reaction in the process in which it flows axially upwardalong the vertical walls 102 through the reformer 10, producing areformed gas mainly containing hydrogen.

The reformed gas thus produced flows axially downward along the verticalwalls 102 through the upstream passage 22 of the reformed gas passage 2,further flows axially upward along the vertical walls 102 through thedownstream passage 23 (arrow D and E in the figure), and reaches the COshifter 15′. In the process in which the reformed gas flows as such,heat retained by the reformed gas is given to the feed gas mixturethrough a shared vertical wall 39 because the upstream passage 22 of thereformed gas passage 2 and the feed gas mixture passage portion 30′ areadjacent to each other with the shared vertical wall 39 interposedtherebetween. Meanwhile, the reformed gas supplied to the CO shifter 15′flows toward the inside of the body, in a radial direction of thecylindrical body-shaped shifter 15′, that is, in a directionperpendicular to the central axis (not shown) of the hydrogen generator(arrow F in the figure). In this process, a shifted gas is producedthrough a shift reaction. Here, since the shift reaction is anexothermic reaction as previously mentioned, the temperature of adownstream end face (i.e., the inner circumferential face) 15′b of theCO shifter 15′ becomes higher than that of an upstream end face (i.e.,the outer circumferential face) 15′a thereof. The shifted gas obtainedfrom the CO shifter 15′ enters the shifted gas passage 3 from thedownstream end face 15′b of the CO shifter 15′, forming a stream such asto collide vertically with the vertical wall 37, which is shared withthe feed gas mixture passage portion 30′ of the reforming materialpassage 1. Then, the shifted gas flows axially upward along the verticalwall 37 through the shifted gas passage 3, and is taken out from theshifted gas outlet port 7 (arrow G in the figure).

In such a configuration, since the feed gas mixture passage portion 30′is adjacent to the vertical wall 37 shared with the shifted gas passage3, heat transfers from the shifted gas, which has a higher temperature,to the feed gas mixture, which has a lower temperature, as inEmbodiment 1. In such a heat exchange, since the shifted gas forms sucha stream as to collide with the vertical wall 37 as described above, noheat transfer laminar film forms in the vicinity of the vertical wall37; therefore, heat exchange from the shifted gas to the feed gasmixture is performed efficiently. In addition, the vertical wall 37 isheated by the radiant heat from the downstream end face 15′b of the COshifter 15′, which has been heated to a higher temperature than that ofthe upstream end face 15′a, and the heat is transferred from thevertical wall 37 to the feed gas mixture.

Thus, the present embodiment makes it possible to improve thermalefficiency by collecting heat from the shifted gas and the CO shifter15′ by the feed gas mixture. Moreover, the effect of trapping the heatgenerated by the shift reaction within the interior of the hydrogengenerator is also attained because the shifted gas is discharged towardthe reformer 10, which is arranged inward of the body. Furthermore, theCO shifter 15′, having a lower temperature than the reformer 10, isarranged on the outer circumference of the reformer 10 so as to cover amajor heat dissipating face of the reformer 10, and the flowingdirection of the gas that passes through the CO shifter 15′ (thedirection perpendicular to the axial direction) is substantiallyperpendicular to the major flowing direction of the gas that passesthrough the reformer 10 (i.e., the axial direction); therefore, thedissipating heat amount from the reformer 10 can be suppressedeffectively.

Still more, here, since the feed gas mixture passage portion 30′ and theupstream passage 22 of the reformed gas passage 2 are directly incontact with each other with the shared vertical wall 39 interposedtherebetween, heat is given from the reformed gas to the feed gasmixture through the vertical wall 39. In addition, the vertical wall 39is heated by the radiant heat from the reformer 10, and the heat istransferred to the feed gas mixture through the vertical wall 39. Thus,in the feed gas mixture and the reformed gas, between which there existsa great temperature difference, heat can be collected from the reformedgas and the reformer 10 by the feed gas mixture. Consequently, such aconfiguration makes it possible to perform heat recovery moreeffectively. Moreover, because heat transfers from the reformed gas tothe feed gas mixture, reducing a heat amount retained by the reformedgas, it becomes feasible at the same time to control the temperature ofthe reformed gas supplied to the CO shifter 15′ at a temperaturesuitable for a shift reaction.

In the foregoing, the reformer 10 has a configuration in which aplatinum group metal is carried on a metal oxide carrier shaped into agranular form, as in Embodiment 1, but it may have a configuration inwhich a platinum group metal is dispersed and carried on a film-statemetal oxide carrier formed on a honeycomb substrate made of ceramic,metal, or the like, depending on the shape of the reformer 10.

Moreover, in the foregoing, the CO shifter 15′ has a configuration inwhich a platinum group metal is carried on a metal oxide carrier shapedinto a granular form; however, depending of the shape of the CO shifter15′, it is possible to adopt a configuration in which a platinum groupmetal is dispersed and carried on a film-state metal oxide carrierformed on a honeycomb substrate made of ceramic, metal, or the like.Furthermore, other than the platinum group metal, a base metal such asCu—Zn type metal may be used as a shift catalyst. It should be notedthat the advantageous effects attained by using a platinum group metalas the catalyst has already been discussed in Embodiment 1.

It should be arbitrary determined whether to employ a configuration inwhich the CO shifter 15′ is arranged on the outer circumference of thereformer 10, as in the present embodiment, or to employ a configurationin which the CO shifter 15 is arranged on an axial end side of thereformer 10, as in Embodiments 1 to 3; nevertheless, it is preferable toselect the appropriate configuration that enlarges the contact areabetween the shifted gas passage 3 and the reforming material passage 1,because the larger contact area enables the more efficient heatexchange. Thereby, the advantageous effects attained by the presentinvention are more effectively exhibited. For example, the reformer 10that constitutes the hydrogen generator is configured to have a longeraxial length than the radial length. For this reason, in such aconfiguration, the configuration in which the CO shifter 15′ is arrangedon the outer circumference of the reformer 10 as in the presentembodiment achieves the larger contact area and is therefore preferable.

[Fuel Cell System]

A fuel cell system according to the present embodiment is constructedsuch that the hydrogen generator of Embodiment 1 included in the fuelcell system of Embodiment 1 (FIG. 5) is replaced by the hydrogengenerator of the present embodiment. This makes it possible to constructa fuel cell system comprising a hydrogen generator that can achieve theforegoing advantageous effects.

It should be noted that although excessive fuel in the fuel cell 151 isused as a fuel gas supplied to the burner 20 in the foregoingEmbodiments 1 to 4, it is also possible to use, for example, otherhydrocarbon-based fuels such as city gas, methane, LP gas, and kerosene,or hydrogen or the like, as the fuel gas. In addition, although town gasis used as a feed gas to be supplied to the reformer 10 in the foregoingEmbodiments 1 to 4, other hydrocarbon-based materials may be used suchas methane, LP gas, methanol, gasoline, or the like.

Furthermore, although the description has been made about cylinder-typehydrogen generators in which cylindrical-shaped gas passages are formedin a concentric circle-like manner in the foregoing Embodiments 1 to 4,the present invention can also be applied to hydrogen generators thathave other shapes.

From the foregoing description, numerous improvements and otherembodiments of the present invention will be readily apparent to thoseskilled in the art. Accordingly, the foregoing description is to beconstrued only as illustrative examples and as being presented for thepurpose of suggesting the best mode for carrying out the invention tothose skilled in the art. Various changes and modifications can be madein specific structures and/or functions substantially without departingfrom the scope and sprit of the invention.

INDUSTRIAL APPLICABILITY

The hydrogen generator according to the present invention is useful as ahydrogen generator used for a fuel cell system or the like.

The fuel cell system according to the present invention is useful as afuel cell system or the like comprising a hydrogen generator in whichits thermal efficiency is improved.

LIST OF REFERENCE NUMERALS

-   1 REFORMING MATERIAL PASSAGE-   2 REFORMED GAS PASSAGE-   3 SHIFTED GAS PASSAGE-   4 COMBUSTION GAS PASSAGE-   5 MATERIAL FEED PORT-   6 WATER SUPPLY PORT-   7 SHIFTED GAS OUTLET PORT-   8 COMBUSTION EXHAUST GAS OUTLET PORT-   9 WATER EVAPORATOR-   10 REFORMER-   15, 15′ CO SHIFTER-   20 BURNER-   21 RADIANT CYLINDER-   30′ FEED GAS MIXTURE PASSAGE PORTION-   32 FEED GAS PASSAGE PORTION-   34 WATER PASSAGE PORTION-   35 HEAT TRANSFER INHIBITING STRUCTURE-   50 BODY-   51 CLEARANCE SPACE-   53 HEAT INSULATOR-   102 VERTICAL WALL-   103 (31) HORIZONTAL WALL-   150 HYDROGEN GENERATOR-   151 FUEL CELL

1. A hydrogen generator comprising a reformer configured to generate areformed gas mainly containing hydrogen from a reforming reactionmaterial through a reforming reaction, a reforming material passageconfigured to supply the reforming reaction material to said reformer, acarbon monoxide shifter configured to lessen carbon monoxide in thereformed gas through a shift reaction, a reformed gas passage configuredto supply the reformed gas from said reformer to said carbon monoxideshifter, and a shifted gas passage configured to take out a shifted gasobtained from said carbon monoxide shifter, characterized in that: saidhydrogen generator is configured to perform heat exchange between saidshifted gas passage and said reforming material passage.
 2. The hydrogengenerator according to claim 1, wherein a heat generating portion ofsaid carbon monoxide shifter faces a wall portion of said shifted gaspassage with a space interposed therebetween.
 3. The hydrogen generatoraccording to claim 1, wherein heat retained by a shifted gas obtainedfrom said carbon monoxide shifter is supplied to said reforming materialgas passage via said shifted gas passage.
 4. The hydrogen generatoraccording to claim 1, wherein said reforming material passage isarranged more inward of said hydrogen generator than said shifted gaspassage.
 5. The hydrogen generator according to claim 1, wherein: aninterior of a body of said hydrogen generator is partitioned by aplurality of axially-directed walls sharing a central axis and arrangedopposing to one another at predetermined gaps, and by a plurality ofradially-directed walls arranged at a predetermined end portion of saidaxially-directed walls so as to intersect with said axially-directedwalls, so that said reforming material passage, said reformed gaspassage, and said shifted gas passage are formed in said body, saidreformer is formed along the central axis, and said carbon monoxideshifter is formed in the axial direction side of said reformer; saidreforming material passage is arranged so as to surround an outer sideof said reformer, one end portion thereof is connected to one end faceof said reformer in the axial direction, and at least a portion thereofis formed along one end face of said reformer in the axial direction;said reformed gas passage is arranged so as to surround an outercircumference of said reformer, one end portion thereof is connected tothe other end face of said reformer in the axial direction, and anotherend portion thereof is connected to an upstream face of said carbonmonoxide shifter; said carbon monoxide shifter is arranged so as tooppose said one end face of said reformer in the axial direction withsaid reforming material passage interposed therebetween; and saidshifted gas passage is connected to a downstream end face of said carbonmonoxide shifter at one end portion thereof, and between said carbonmonoxide shifter and said reformer opposing each other, said shifted gaspassage is directly or indirectly in contact with a portion of saidreforming material passage that is along the end face of said reformer.6. The hydrogen generator according to claim 1, wherein: an interior ofa body of said hydrogen generator is partitioned by a plurality ofaxially-directed walls sharing a central axis and arranged opposing toone another at predetermined gaps, and by a plurality ofradially-directed walls arranged at a predetermined end portion of saidaxially-directed walls so as to intersect with said axially-directedwalls, so that said reforming material passage, said reformed gaspassage, and said shifted gas passage are formed in said body, saidreformer is formed along the central axis, and said carbon monoxideshifter is formed so as to surround an outer side of said reformer inthe axial direction; said reforming material passage is arranged so asto surround an outer side of said reformer, and one end portion thereofis connected to one end face of said reformer in the axial direction;said reformed gas passage is arranged so as to surround an outer side ofsaid reforming material passage in the axial direction, one end portionthereof is connected to the other end face of said reformer in the axialdirection, and the other end portion thereof is connected to an upstreamface of said carbon monoxide shifter; said carbon monoxide shifter ispositioned between said reformed gas passage and said reforming materialpassage and is arranged so as to surround said reforming materialpassage in the axial direction; and said shifted gas passage isconnected to a downstream end face of said carbon monoxide shifter atone end portion thereof, said shifted gas passage is directly orindirectly in contact with said reforming material passage between saidcarbon monoxide shifter and said reformer, and said shifted gas passagesurrounds an outer side of said reforming material passage in the axialdirection.
 7. The hydrogen generator according to claim 5, wherein theshifted gas is discharged from the downstream end face of said carbonmonoxide shifter into said shifted gas passage so as to collide with, atthe portion where said shifted gas passage and said reforming materialpassage are in contact, a partition wall that partitions both of saidpassages, and thereafter, the shifted gas travels along said shifted gaspassage.
 8. The hydrogen generator according to claim 5, wherein, insaid carbon monoxide shifter, a gas traveling direction from saidupstream face toward said downstream end face is substantially avertical direction.
 9. The hydrogen generator according to claim 5,wherein: the reforming reaction material contains a hydrocarbon-basedfeed gas and water, and said reforming material passage comprises apassage portion in which the feed gas and water travel in differentphase states, a water evaporator configured to evaporate the water toproduce steam, and a feed gas mixture passage portion in which a gasmixture of the feed gas and the steam travels; and said reformingmaterial passage that is directly or indirectly in contact with saidshifted gas passage is said feed gas mixture passage portion.
 10. Thehydrogen generator according to claim 5, wherein: the reforming reactionmaterial contains a hydrocarbon-based feed gas and water, and saidreforming material passage comprises a passage portion in which the feedgas and water travel in different phase states, a water evaporatorconfigured to evaporate the water to produce steam, and a feed gasmixture passage portion in which a gas mixture of the feed gas and thesteam travels; and said reforming material passage that is directly orindirectly in contact with said shifted gas passage is said passageportion in which the feed gas and water travel in different phasestates.
 11. The hydrogen generator according to claim 5, wherein: thereforming reaction material contains a hydrocarbon-based feed gas andwater, and said reforming material passage comprises a feed gas passageportion in which only the feed gas travels, a passage portion in whichthe feed gas and water travel in different phase states, a waterevaporator configured to evaporate the water to produce steam, and afeed gas mixture passage portion in which a gas mixture of the feed gasand the steam travels; and said reforming material passage that isdirectly or indirectly in contact with said shifted gas passage is saidfeed gas passage portion.
 12. The hydrogen generator according to claim5, wherein: the reforming reaction material contains a hydrocarbon-basedfeed gas and water, and said reforming material passage comprises awater passage portion in which only the water travels, a passage portionin which the water and the feed gas travel in different phase states, awater evaporator configured to evaporate the water to produce steam, anda feed gas mixture passage portion in which a gas mixture of the feedgas and the steam travels; and said reforming material passage that isdirectly or indirectly in contact with said shifted gas passage is saidwater passage portion.
 13. The hydrogen generator according to claim 1,wherein said carbon monoxide shifter is such that a platinum group metalserving as a shift catalyst is carried on a carrier composed of a metaloxide containing at least one selected from Al, Ce, and Zr.
 14. Thehydrogen generator according to claim 1, configured to perform heatexchange between said reformed gas passage and said reforming materialpassage.
 15. A fuel cell system, characterized by comprising: a hydrogengenerator according to claims 1 through 14; and a fuel cell configuredto generate power using a fuel gas and an oxidizing gas, the fuel gascontaining hydrogen as its main component and being supplied from saidhydrogen generator.